Components and catalysts for the polymerization of olefins

ABSTRACT

Components and catalysts for the polymerization of olefins comprising the product obtained by contacting a compound of a transition metal M, containing at least one M-π bond, with an olefinic prepolymer obtained by polymerization of one or more olefins with a coordination catalyst comprising a compound of Ti or V supported on a magnesium halide.

This is a divisional of U.S. application Ser. No. 08/409,846, filed Mar.27, 1995, now U.S. Pat. No. 5,759,940.

The present invention relates to components of catalysts for thepolymerization of olefins, the catalysts obtained from them and the useof said catalysts in the polymerization of olefins CH₂ ═CHR in which Ris hydrogen or an alkyl, cycloalkyl or aryl radical with 1-12 carbonatoms.

Another aspect of the present invention relates to the polymers obtainedusing said catalysts.

Coordination catalysts obtained from compounds ML_(x), in which M is atransition metal and in particular Ti, Zr and Hf, L is a ligandcoordinating the metal, x is the valence of the metal and at least oneof the ligands L has cyclo-alkadienyl structure, are known from theliterature. Catalysts of this type using compounds Cp₂ TiCl₂ or Cp₂ZrCl₂ (Cp=cyclopentadienyl) are described in U.S. Pat. Nos. 2,827,446and 2,924,593. The compounds are used together with Al-alkyl compoundsin the polymerization of ethylene. The catalytic activity is very low.Catalysts with very high activity are obtained from compounds Cp₂ ZrCl₂or Cp₂ TiCl₂ and from their derivatives substituted in thecyclopentadienyl ring, in which the Cp ring can also be condensed withother rings, and from polyalumoxane compounds containing the repeatingunit --(R)AlO--, in which R is lower alkyl, preferably methyl (U.S. Pat.No. 4,542,199 and EP-A-129368).

Catalysts of the aforementioned type in which the metallocene compoundcontains two indenyl or tetrahydroindenyl rings bridge-bonded throughlower alkylenes or through other divalent radicals are suitable forpreparation of stereoregular polymers of propylene and of other alphaolefins (EP-A-185918).

Stereospecific catalysts are also obtained from dicyclopentadienylcompounds in which the two rings are substituted in various ways withgroups with steric hindrance so as to prevent rotation of the ringsabout the axis of coordination with the metal.

Substitution of indenyl or tetrahydroindenyl at suitable positions ofthe pentadienyl ring gives catalysts that have very highstereospecificity (EP-A-485823, EP-A-485820, EP-A-519237, U.S. Pat. No.5,132,262 and U.S. Pat. No. 5,162,278).

The metallocene catalysts described above yield polymers with verynarrow molecular weight distribution (Mw/Mn around 2).

Some of these catalysts also have the property of forming copolymers ofethylene with alpha olefins of the LLDPE type or ethylene/propyleneelastomeric copolymers with very uniform distribution of the comonomerunits. The LLDPE polyethylene obtained is further characterized by lowsolubility in solvents such as xylene or n-decane.

The polypropylene obtained with the more stereospecific catalystsmentioned above exhibits increased crystallinity and a higherdeformation temperature compared with the polymer that can be obtainedwith conventional Ziegler-Natta catalysts.

However, these metallocene catalysts present a notable difficulty withrespect to the possibility of being used in industrial processes forproduction of polyolefins that are not carried out in solution, due tothe fact that they are soluble in the reaction medium in which they areprepared and in the liquid polymerization medium.

In order to be able to use them in polymerization processes that are notperformed in solution, the catalysts must be supported on suitablesupports which endow the polymer with appropriate morphologicalproperties.

Many kinds of supports are used including, among others, porous metaloxides such as silica or porous polymeric supports such as polyethylene,polypropylene and polystyrene. Magnesium halides are also used assupport. In some cases they are also used as counter-ions of an ion pairin which the metallocene compound supplies the cation and a compound ofthe Mg halide type supplies the anion.

Use of a support tends, however, to lower the activity of the catalystsconsiderably. Japanese application No. 168408/88 (published Dec. 7,1988) describes the use of magnesium chloride as support of metallocenecompounds of the type Cp₂ TiCl₂, Cp₂ ZrCl₂, Cp₂ Ti(CH₃)₂ for forming,with Al-trialkyl and/or polymethylalumoxane (MAO), catalysts forpolymerization of ethylene. The component comprising the magnesiumchloride is prepared by grinding it together with the metallocenecompound, also working in the presence of electron-donor compounds orsupporting the metallocene on a suitable liquid adduct of MgCl₂ with analcohol and subsequent reaction with AlEt₂ Cl. The catalysts do not havesufficiently high activity with respect to MgCl₂.

Catalysts comprising a metallocene compound of the Cp₂ ZrCl₂ typesupported on MgCl₂ in spherical form and partially complexed with anelectron-donor compound are described in U.S. Pat. No. 5,106,804.

The performance of these catalysts is better than that described inJapanese application No. 168408/88 but is still not such as to permitthe production of polymers containing low enough catalyst residues. Thequantity of Zr compound supported on MgCl₂ is relatively low (the Zr/Mgratio in the catalyst is less than about 0.05).

Furthermore, the catalysts require the use of polymethylalumoxane (MAO)and are not active with Al-alkyls of the Al-triethyl type. However, theyields relative to MAO are not high.

Application EP-A-318048 describes catalysts in which a solid componentcomprising a Ti compound supported on a magnesium chloride that hasparticular characteristics of surface area and porosity and if necessaryan electron-donor compound, is used with benzylic compounds of Ti or Zror with metallocene compounds of the type Cp2Ti(CH₃)₂ andbis-(indenyl)-Zr(CH₃)₂ to form catalysts for polymerization of ethyleneand of propylene. The ratio by weight of metallocene to magnesiumchloride is very high (greater than 1) so that it is necessary to removethe metallocene from the polymer that is obtained. The catalysts areused in processes carried out in the presence of a liquid polymerizationmedium.

Application EP-A-439964 describes bimetallic catalysts suitable forpreparation of ethylene polymers with wide molecular weight distribution(Mw/Mn between 4 and 14) obtained by supporting a metallocene on a solidcomponent containing a Ti compound supported on magnesium chloride. MAOor its mixtures with Al-alkyl are used as co-catalyst. Al-trialkyls arealso used on their own, but the catalytic activity is low. The yields ofthese mixed catalysts in which active centres are operative, derivedboth from the Ti compound supported on MgCl₂ and from the metallocenecompound, are very high when the catalysts are used in a hydrocarbonmedium; on the other hand they are low when polymerization is carriedout in the gas phase.

Application EP-A-522281 describes catalysts obtained from Cp₂ ZrCl₂supported on magnesium chloride and from mixtures of Al-trialkyl andcompounds supplying stable anions of thedimethylanilino-tetrakis-(pentafluorophenyl)borate type. The catalystsare prepared by grinding the components and are used in polymerizationtests in the presence of a solvent (toluene) with yields of polyethylenerelative to MgCl₂ of the order of 9000 g/g.

Application EP-A-509944 describes catalysts using compounds of theanilino-tetrakis-(pentafluorophenyl)borate type or Lewis acids such asMgCl₂ together with metallocene halides pre-reacted with Al-alkylcompounds.

The magnesium chloride is ground before it is brought into contact withthe pre-reacted metallocene compound. The yields of polymer relative tothe Mg halide are not high. Catalyst components have now been found thatare able to form catalysts with particularly high activity and that arecapable of producing polymers with controlled morphological propertiesso that the catalysts can also be used in gas-phase processes in afluidized bed.

The components of the invention are obtained by bringing a compound of atransition metal M selected from Ti, V, Zr and Hf containing at leastone M-π bond into contact with a prepolymer obtained by polymerizationof one or more olefins CH₂ ═CHR in which R is hydrogen or an alkyl,cycloalkyl or aryl with 1-12 carbon atoms, and/or of one or more di- orpolyenes, with a coordination catalyst comprising the product obtainedby contacting a compound of Ti, V, Zr, Hf or mixture thereof with a Mghalide in the form of particles with average size of the crystallitesbelow 300 Å. The polymeric support is prepared in a quantity of from 0.5to 2000 g per g of solid component, preferably in a quantity of from 5to 500 g per g, and more preferably in a quantity of from 10 to 100 gper g of solid component. The compound of the transition metal Mincludes in particular at least one ligand L coordinated on the metal Mpossessing a mono- or polycyclic structure containing conjugated πelectrons. Said compound of the transition metal M is preferably chosenfrom among compounds with the structure:

    Cp.sup.I MR.sup.1.sub.a R.sup.2.sub.b R.sup.3.sub.c        (I)

    Cp.sup.I Cp.sup.II MR.sup.1.sub.a R.sup.2.sub.b            (II)

    (Cp.sup.I --A.sub.e --Cp.sup.II)M.sup.1 R.sup.1.sub.a R.sup.2.sub.b(III)

in which M is Ti, V, Zr or Hf; Cp^(I) and Cp^(II), which may beidentical or different from each other, are cyclopentadienyl groupswhich may be substituted; two or more substituents on the saidcyclopentadienyl groups can form one or more rings having from 4 to 6carbon atoms; R¹, R² and R³, which may be identical or different, areatoms of hydrogen, halogen, an alkyl or alkoxyl group with 1-20 carbonatoms, aryl, alkaryl, or aralkyl with 6-20 carbon atoms, an acyloxygroup with 1-20 carbon atoms, an allyl group, or a substituentcontaining a silicon atom; A is an alkenyl bridge or has a structurechosen from: ##STR1## ═BR₁, ═AlR₁, --Ge--, --Sn--, --O--, --S--, ═SO,═SO₂, ═NR₁, ═PR₁, or ═P(O)R₁, in which M₁ is Si, Ge, or Sn; R₁ and R₂,which may be identical or different, are alkyl groups with 1-4 carbonatoms or aryl groups with 6-10 carbon atoms; a, b, c are, independently,integers from 0 to 4; e is an integer from 1 to 6 and two or more of theradicals R¹, R² and R³ can form a ring. In the case when the group Cp issubstituted, the substituent is preferably an alkyl group with 1-20carbon atoms.

Representative compounds possessing formula (I) include:

(Me₅ Cp)MMe₃, (Me₅ Cp)M(OMe)₃, (Me₅ Cp)MCl₃, (Cp)MCl₃, (Cp)MMe₃,(MeCp)MMe₃, (Me₃ Cp)MMe₃, (Me₄ Cp)MCl₃, (Ind)MBenz₃, (H₄ Ind)MBenz₃,(Cp)MBu₃.

Representative compounds possessing formula (II) include:

(Cp)₂ MMe₂, (Cp)₂ MPh₂, (Cp)₂ MEt₂, (Cp)₂ MCl₂, (Cp)₂ M(OMe)₂, (Cp)₂M(OMe)Cl, (MeCp)₂ MCl₂, (Me₅ Cp)₂ MCl₂, (Me₅ Cp)₂ MMe₂, (Me₅ Cp)₂ MMeCl,(Cp)(Me₅ Cp)MCl₂, (1-MeFlu)₂ MCl₂, (BuCp)₂ MCl₂, (Me₃ Cp)₂ MCl₂, (Me₄Cp)₂ MCl₂, (Me₅ Cp)₂ M(OMe)₂, (Me₅ Cp)₂ M(OH)Cl, (Me₅ Cp)₂ M(OH)₂, (Me₅Cp)₂ M(C₆ H₅)₂, (Me₅ Cp)₂ M(CH₃)Cl, (EtMe₄ Cp)₂ MCl₂, [(C₆ H₅)Me₄ Cp]₂MCl₂, (Et₅ Cp)₂ MCl₂, (Me₅ Cp)₂ M(C₆ H₅)Cl, (Ind)₂ MCl₂, (Ind)₂ MMe₂,(H₄ Ind)₂ MCl₂, (H₄ Ind)₂ MMe₂, {[Si(CH₃)₃ ]Cp}₂ MCl₂, {[Si(CH₃)₃ ]₂Cp}₂ MCl₂ 1 (Me₄ Cp)(Me₅ Cp)MCl₂,

Representative compounds possessing formula (III) include:

C₂ H₄ (Ind)₂ MCl₂, C₂ H₄ (Ind)₂ MMe₂, C₂ H₄ (H₄ Ind)₂ MCl₂, C₂ H₄ (H₄Ind)₂ MMe₂, Me₂ Si(Me₄ Cp)₂ MCl₂, Me₂ Si(Me₄ Cp)₂ MMe₂, Me₂ SiCp₂ MCl₂,Me₂ SiCp₂ MMe₂, Me₂ Si(Me₄ Cp)₂ MMeOMe, Me₂ Si(Flu)₂ MCl₂, Me₂Si(2-Et-5-iPrCp)MCl₂, Me₂ Si(H₄ 1nd)₂ MCl₂, Me₂ Si(H₄ Flu)₂ MCl₂, Me₂SiCH₂ (Ind)₂ MCl₂, Me₂ Si(2-Me-H₄ Ind)₂ MCl₂, Me₂ Si(2-MeInd)₂ MCl₂, Me₂Si(2-Et-5-iPr-Cp)₂ MCl₂, Me₂ Si(2-Me-5-EtCp)₂ MCl₂, Me₂Si(2-Me-5-Me-Cp)₂ MCl₂, Me₂ Si(2-Me-4,5-benzoindenyl)₂ MCl₂, Me₂Si(2-EtInd)₂ MCl₂, Me₂ Si(4,5-benzoindenyl)₂ MCl₂, Me₂Si(2-t-butyl-Ind)MCl₂, Me₂ Si(2-iPr-Ind)₂ MCl₂, Me₂Si(3-t-butyl-5-MeCp)₂ MCl₂, Me₂ Si(3-t-butyl-5-MeCp)₂ MMe₂, Me₂Si(2-MeInd)₂ MCl₂, C₂ H₄ (2-Me-4,5-benzoindenyl)₂ MCl₂, Me₂C(Flu)CpMCl₂, Ph₂ Si(Ind)₂ MCl₂, Ph(Me)Si(Ind)₂ MCl₂, C₂ H₄ (H₄Ind)M(NMe₂)OMe, isopropylidene-(3-t-butylCp)(Flu)MCl₂, Me₂ C(Me₄Cp)(MeCp)MCl₂ MeSi(Ind)₂ MCl₂, Me₂ Si(Ind)₂ MMe₂, Me₂ Si(Me₄ Cp)₂MCl(OEt), C₂ H₄ (Ind)₂ M(NMe₂)₂, C₂ H₄ (Me₄ Cp)₂ MCl₂, C₂ Me₄ (Ind)₂MCl₂, Me₂ Si(3-Me-Ind)₂ MCl₂, C₂ H₄ (2-Me-Ind)₂ MCl₂, C₂ H₄ (3-Me-Ind)₂MCl₂, C₂ H₄ (4,7-Me₂ -Ind)₂ MCl₂, C₂ H₄ (5,6-Me₂ -Ind)₂ MCl₂, C₂ H₄(2,4,7-Me₃ Ind)₂ MCl₂, C₂ H₄ (3,4,7-Me₃ Ind)₂ MCl₂, C₂ H₄ (2-Me-H₄ 1nd)₂MCl₂, H₄ (4,7-Me₂ -H₄ Ind)₂ MCl₂, C₂ H₄ (2,4,7-Me₃ -H₄ Ind)₂ MCl₂, Me₂Si(4,7-Me₂ -Ind)₂ MCl₂, Me₂ Si(5,6-Me₂ -7nd)₂ MCl₂, Me₂ Si(2,4,7-Me₃ -H₄1nd)₂ MCl₂.

In the simplified formulae given above, the symbols have the followingmeanings:

Me=methyl, Et=ethyl, iPr=isopropyl, Bu=butyl, Ph=phenyl,Cp=cyclopentadienyl, Ind=indenyl, H₄ Ind=4,5,6,7-tetrahydroindenyl,Flu=fluorenyl, Benz=benzyl, M=Ti, Zr or Hf, preferably Zr.

Compounds of the type Me₂ Si(2-Me-Ind)₂ ZrCl₂ and Me₂ Si(2-Me-H₄Ind)ZrCl₂ and their methods of preparation are described in Europeanapplications EP-A-485822 and 485820 respectively, the descriptions ofwhich are included here by reference.

Compounds of the type Me₂ Si(3-t-butyl-5-MeCp)₂ ZrCl₂ and of the typeMe₂ Si(2-Me-4,5-benzoindenyl)ZrCl₂ and their method of preparation aredescribed in patent U.S. Pat. No. 5,132,262 and in patent applicationEP-A-549900 respectively, the descriptions of which are included here byreference.

The catalysts used for preparation of the prepolymer preferably comprisethe product obtained by contacting a halide of Ti, V, Zr, Hf or mixturethereof, especially a chloride or a halogen-alcoholate of Ti or V, witha Mg chloride having average size of the crystallites below 300 Å andpreferably below 150 Å and more preferably in the range from about 30 to120 Å. The chlorides and the halogen-alcoholates of Ti or V preferablyinclude TiCl₄, TiCl₃, chloro-alcoholates of Ti such as Ti(OBu)₂ Cl₂ andTi(OBu)Cl₃, VCl₃, VOCl₃.

Examples of catalysts of this type are described in patents U.S. Pat.No. 4,495,338, U.S. Pat. No. 4,298,718 and U.S. Pat. No. 4,542,198, thedescriptions of which are included here by reference. Other examples ofcatalysts comprising the product obtained by contacting one or morecompounds of Ti, V, Zr or Hf with a magnesium halide having the abovespecified features are given in Italian Patent ApplicationsMI-94-A-001065 and MI-94-A-001421. Preferably, the solid components ofthe catalysts are used in spherical form with particle size from approx.5 to 100 microns and with surface area greater than 200 m² /g (BET) andporosity (nitrogen method) greater than 0.3 cc/g or with surface area(BET) less than 200 m² /g and porosity (mercury method) between about0.5 cc/g and 2 cc/g.

Examples of catalysts comprising components of this type and the methodof preparation of the components are described in patents U.S. Pat. No.4,399,054, EP-A-395083, EP-A-553805 and EP-A-553806, the descriptions ofwhich are included here by reference. The content of titanium orvanadium in the said catalytic components is preferably greater than 1%by weight and preferably between 2 and 10% by weight.

The catalysts preferably use as Al-alkyl compound, an Al-trialkyl suchas AlEt₃, Al-triisobutyl, Al-tri-n-butyl, and their mixtures withAl-dialkyl halides. Alumoxane compounds can also be used. The olefinsused in preparation of the prepolymer include ethylene, propylene,1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene and their mixtures.

Preferably the prepolymer is made up of polyethylene, copolymers ofethylene with proportions less than 20 mol. % of an olefin selected frompropylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene,cyclopentene, cyclohexene; polypropylene with isotacticity index above80%; crystalline copolymers of propylene with smaller amounts (5 mol. %or less) of ethylene and/or a-olefins such as 1-butene, 1-hexene.Prepolymers from dienes or conjugated polyenes can also be used.

Prepolymerization is preferably carried out in liquid phase consistingof an inert hydrocarbon solvent such as propane, hexane, heptane,isobutane or of a monomer, or in gas phase working at temperaturesgenerally below 100° C., and preferably between 20° C. and 70° C.

The prepolymer is produced in a quantity greater than about 0.5 g per gof component and up to about 2000 g/g. Preferably the amount is between5 and 500 g per g of solid component, and more preferably between 10 and100 g per gram of solid component.

The porosity of the prepolymer, determined with the mercury methoddescribed hereinafter, is preferably greater than 0.3 cm³ /g, morepreferably greater than 0.4 cm³ /g and expecially greater than 0.5 cm³/g. The above given porosity values refer to pores having radius up to50,000 Å.

The quantity of magnesium halide present in the prepolymer, expressed asMg, is generally between 50 and 50000 ppm, preferably between 100 and20000 ppm, and more preferably between 300 and 10000 ppm.

The atomic ratio of the transition metal M containing at least one 7bond with the magnesium of the halide, in particular the Zr/Mg ratio(relative to the Zr compound present in the prepolymer such as cannot beextracted with toluene: 3 washings at a concentration of 100 g/liter at20° C.) is greater than 0.1, in particular greater than 0.2 andpreferably between 0.3 and 3.

Transition metal/magnesium atomic ratios above 0.1 have never beforebeen accomplished in the components comprising an Mg halide and ametallocene compound of Zr, Ti, V or Hf. Catalytic components comprisinga prepolymer containing dispersed fine particles of Mg halide and whichcontain, in a form at least partly combined with the Mg halide, acompound of a transition metal M chosen from among Ti, V, Zr or Hfcontaining at least one M-x bond, in an atomic ratio M/Mg greater than0.1, have not been described previously in the literature. The reactionof the prepolymer containing the solid component of theprepolymerization catalyst with the transition metal compound ispreferably carried out an inert hydrocarbon medium in which themetallocene compound is soluble (toluene, benzene and similarhydrocarbons), working at temperatures between -40° C. and the meltingpoint of the prepolymer, preferably between 0 and 100° C., and morepreferably between 10 and 70° C.

The reaction between the prepolymer and the transition metal compoundcontaining at least one ; bond can if necessary be effected in thepresence of an electron-donor compound in such a way as to fix aquantity of electron-donor compound between 0.1 and 15 wt. % of thetotal.

The solubility of the metallocene compound containing at least one M-πbond increases when the said compound is dissolved in toluene andsimilar hydrocarbons also containing dissolved therein Al-alkyl compoundsuch as Al-triethyl, Al-triisobutyl or a polyalkylalumoxane, and inparticular MAO or its mixtures with an Al-alkyl compound, using molarratios of Al-alkyl compound/metallocene compound greater than 2,preferably between 5 and 100. The solutions that are obtained areparticularly suitable as components of catalyst having very highactivity. Such activity is greater than the activity that can beobtained when using solutions of the metallocene compound that have beenobtain ed in the absence of the Al compound mentioned above.

The components of the invention form, with Al-alkyl compounds or withpolyalkylalumoxane compounds or their mixtures, catalysts that have veryhigh activity relative to the Mg halide, by far greater than that of thecatalysts containing Mg halide known up to now.

The Al-alkyl compound is generally selected from among compounds offormula AlR₃, in which R is an alkyl with 1-12 carbon atoms, and thealumoxane compounds containing the repeating unit --(R⁴)AlO--, in whichR⁴ is an alkyl radical containing from 1 to 6 carbon atoms, and saidalumoxane compounds contain from 2 to 50 repeating units possessing theformula described above. Typical examples of compounds with the formulaAlR₃ are Al-trimethyl, Al-triethyl, Al-triisobutyl, i-tri-n-butyl,Al-trihexyl and Al-trioctyl. Among the alumoxane compounds, use of MAOis preferred. Mixtures of Al-alkyl compounds, preferably Al-triisobutyl,and alumoxane compounds, preferably MAO, are also used advantageously.

When the transition metal compound containing at least one M-π bond isof the type described in formulae (II) and (III), the compounds obtainedfrom reaction between AlR₃ and H₂ O in molar ratios between 0.01 and 0.5can be used advantageously.

Activities of at least 100 kg/g of MgCl₂ and which can even be greaterthan 1000 kg/g of MgCl₂ can normally be obtained even in gas-phasepolymerization processes. Using prepolymers obtained with catalystswhose components are in the form of spherical particles, it is possibleto obtain polymers which replicate the morphology of the catalystcomponent and hence conduct processes in the gas phase in a fluidizedbed in an easily controllable manner, avoiding difficulties such aslocal overheating of the bed, problems with heat exchange etc., whichmake it difficult to conduct processes in the gas phase.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a photograph of the catalyst reproduced at 12-timesmagnification;

FIG. 2 shows a photograph of the polymer obtained by polymerization inthe gas phase, reproduced at 3.5 times magnification.

Moreover, it is possible, using prepolymers obtained with catalystswhose components are in the form of spherical particles that have highmacroporosity (e.g. Hg porosity greater than 1 cc/g), to produce in thegas-phase polymers and copolymers of a rubbery nature, which normallytend to agglomerate and create problems in conducting the gas-phaseprocess.

The catalysts of the invention can be used for (co)polymerization ofolefins CH₂ ═CHR, where R is hydrogen or an alkyl radical with 1-10carbon atoms or an aryl.

They are used in particular for polymerization of ethylene and itsmixtures with alpha olefins of the type indicated above, in which R isan alkyl radical.

The catalysts, especially those obtained from compounds of the type C₂H₄ (Ind)₂ ZrCl₂, C₂ H₄ (H₄ Ind)ZrCl₂ and Me₂ Si(Me₄ Cp)₂ ZrCl₂ aresuitable for producing LLPDE (copolymers of ethylene containing smallerproportions, generally less than 20 mol. %, of C₃ -C₁₂ alpha olefin)characterized by relatively low density values relative to the contentof alpha olefin, with reduced solubility in xylene at room temperature(below approx. 10 wt. %) and with molecular weight distribution Mw/Mnbetween about 2.5 and 5.

For a density of 0.912 the content of α-olefin is equal to about 5 mol.%. For a density of 0.906 the content of α-olefin is equal to about 7mol. %.

The Mw/Mn values are generally higher than those obtainable with themetallocene catalysts known hitherto, whether used in solution orsupported, and endow the polymer with characteristics of processabilitythat are superior to those of polymers that have a narrower molecularweight distribution.

The polypropylenes that can be obtained with catalysts that use a chiralmetallocene compound are characterized by high stereoregularity, withhigh molecular weights that are easily controllable and with highcrystallinity.

The chiral metallocene compounds that can be used are, for example, ofthe type described in European application EP-A-485823, EP-A-485820,EP-A-519237, and U.S. Pat. Nos. 5,132,262, and 5,162,278.

The following examples are given to illustrate the invention and arenon-restricting. The properties stated were determined according to thefollowing methods:

Porosity and Surface Area with Nitrogen

determined according to the B.E.T. methodology (apparatus used:SORPTOMATIC 1800 from Carlo Erba).

POROSITY AND SURFACE AREA WITH MERCURY:

determined by immersing a known quantity of the sample in a knownquantity of mercury inside a dilatometer and then gradually increasingthe mercury pressure hydraulically. The pressure of penetration ofmercury into the pores is a function of their diameter. Measurement iseffected using a "Porosimeter 2000 series" porosimeter from Carlo Erba.The porosity, pore distribution and surface area are calculated from thedata for the decrease of volume of the mercury and from the values ofthe applied pressure.

PARTICLE SIZE OF THE CATALYST:

determined with a method based on the principle of optical diffractionof monochromatic laser light with the "Malvern Instr. 2600" apparatus.The mean size is stated as P50.

MIE FLOW INDEX:

ASTM-D 1238, condition E

MIF FLOW INDEX:

ASTM-D 1238, condition F

FLOWABILITY:

is the time taken by 100 g of polymer to flow through a funnel whoseoutlet has a diameter of 1.25 cm and whose walls are inclined 20° fromthe vertical.

APPARENT DENSITY:

DIN-53194

MORPHOLOGY AND GRANULOMETRIC DISTRIBUTION OF THE POLYMER PARTICLES:

ASTM-D 1921-63

FRACTION SOLUBLE IN XYLENE:

determined at 25° C.

CONTENT OF COMONOMER:

percentage by weight of comonomer determined from IR spectrum.

ACTUAL DENSITY:

ASTM-D 792

MEAN SIZE OF CRYSTALLITES D(110):

determined by measuring the width at half-height of the (110)diffraction line that appears in the X-ray spectrum of the magnesiumhalide, applying Scherrer's equation:

    D(110)=(K·1.542·57.3)/(B-b)cos θ,

where: K=constant (1.83 in the case of magnesium chloride);

B=width at half-height (in degrees) of the (110) diffraction line;

b=instrumental broadening;

θ=Bragg angle.

In the case of magnesium chloride, the (110) diffraction line appears atan angle 2θ of 50.2°.

EXAMPLES

In the examples the percentages are by weight. The term catalyst denotesthe component obtained by bringing the transition metal compound intocontact with the prepolymer. The term support denotes the prepolymerused in preparation of the catalyst. The intrinsic viscosity isexpressed in dl/g.

Example 1

Preparation of the support

10 liters of hexane were loaded into a glass autoclave equipped withanchor stirrer and baffles, with capacity of 25 liters and treated withN₂ at 90° C. for 3 hours. 290 g of catalyst prepared according to themethod described in example 3 of patent EP-A-553806 and with an averagediameter of 30 μm were added, while stirring at 20° C. Then 2.0 litersof a solution of Al-triisobutyl (TIBAL) in hexane (100 g/l) wereintroduced in 15 minutes at 20° C. and stirring was continued for 15minutes. Ethylene was supplied at a partial pressure of 100 mmHg at 35°C. and polymerization was effected until a yield equal to 40 g ofpolymer per gram of solid catalyst component was obtained. Threewashings were effected in hexane 100 g/liter at 20° C. After drying,11.6 kg of spherical prepolymer was obtained, with the followingcharacteristics:

Surface area=1.6 m² /g (Hg);

Porosity=0.702 cm³ /g (Hg; referred to pores with radius up to 50,000Å);

P50=131.33 μm;

Ti=0.2%; Cl=1.1%; Mg=0.26%; Al=0.05%.

Preparation of the metallocene/polymethylalumoxane solution

A 1000 cm³ reactor, equipped with anchor stirrer and treated with N₂,was loaded with 600 cm³ of toluene, 47.4 g of polymethylalumoxane (MAO)and 8.46 g of ethylene-bis-(indenyl)-zirconium dichloride (EBI). Thesystem was stirred continuously in N₂ atmosphere at 20° C. for 3 hour.At the end of this period a clear solution was obtained.

Preparation of the catalyst

A 1000 cm³ reactor, equipped with anchor stirrer and treated with N₂ at90° C. for 3 hours, was loaded, in nitrogen atmosphere at 20° C., with300 cm³ of toluene, and 100 g of the support previously prepared. 200Cm³ of the previously prepared metallocene/MAO solution was introducedin lb minutes at 20° C. while stirring. The system was brought up to 40°C. and maintained at that temperature for 4 hours and then the solventwas removed by vacuum evaporation at a maximum temperature of about 40°C. for about 3 hours. 118.62 g of spherical catalyst was obtained, withthe following characteristics:

Zr=0.5%; Mg=0.26%; Cl=1.28%; Al=5.2%.

Polymerization (HDPE)

In a glass flask treated with N₂ at 90° C. for 3 hours, 0.42 g of MAOand 0.05 g of the catalyst described above were pre-contacted in 100 cm³of toluene, for 5 minutes at 30° C.

Then the whole was fed into a 4-liter steel autoclave, equipped withanchor stirrer and treated with N₂ at 90° C. for 3 hours, containing 1.6liters of hexane at approx. 20° C. The autoclave was raised to 75° C.and 7 bar of ethylene and 0.1 bar of hydrogen were supplied.Polymerization was effected for one hour, keeping the temperature andethylene pressure constant.

Polymerization was discontinued by instantaneous degassing of theautoclave and, after cooling to 20° C., the slurry of polymer wasdischarged and dried in oven at 80° C. in nitrogen. 325 g ofpolyethylene in the form of spherical particles was obtained (yield 6500g polyethylene/g cat; 1300 kg/g Zr; 640 kg/g MgCl₂), with the followingcharacteristics:

MIE=0.8; F/E=62; η=1.1; Mw/Mn=3,4

Example 2

Polymerization (LLDPE)

In a glass flask treated with N₂ at 90° C. for 3 hours, 0.42 g of MAOand 0.05 g of the catalyst from example 1 were pre-contacted in 100 cm³of toluene, for 5 minutes at 20° C.

Then the whole was fed into a 4-liter steel autoclave, equipped withanchor stirrer and treated in N₂ at 90° C. for three hours, containing800 g of propane at 30° C. The autoclave was heated to 75° C. and 0.1bar of H₂ was supplied, and then, simultaneously 7 bar of ethylene, and100 g of 1-butene. Polymerization was effected for 1 hour, keeping thetemperature and the ethylene pressure constant. 125 g of ethylene-butenecopolymer in the form of spherical particles was obtained (yield 2500 ofcopolymer/g cat; 500 kg/g Zr; 245 kg/g MgCl₂) with the followingcharacteristics:

MIE=8.4; F/E=19; η=1; actual density=0.912; bound butene=11%; insolublesin xylene=94%; Mw/Mn=2.8.

Example 3

Polymerization (LLPDE)

0.05 g of the catalyst of example 1 was pre-contacted under the sameconditions as in example 2 using 1.4 g of TIBAL instead of 0.42 of MAO.Then ethylene and butene were copolymerized in the same conditions as inexample 2. 75 g of ethylene-butene copolymer was obtained (yield 1500 gcopolymer/g catalyst), with the following characteristics:

MIE=3; F/E=35.3; η=1.1; actual density=0.912; insolubles in xylene=90%.

Example 4

Preparation of the support

Same procedure as in example 1.

Preparation of the metallocene/MAO solution

The conditions were the same as in example 1 but with the followingquantities of reactants: 300 cm³ toluene; 43.26 g of MAO; 19.58 g ofEBI.

Preparation of the catalyst

The conditions were the same as in example 1, but with 100 cm³ of themetallocene/MAO solution. Approx. 118 g of spherical catalyst wasobtained, with the following characteristics:

Zr=0.77%; Mg=0.17%; Cl=1.35%; Al=3.95%.

Polymerization

The polymerization conditions were identical to example 2 but instead of0.1 bar of H₂ and 100 g of butene, 0.5 bar of H₂ and 150 g of butenewere used. 350 g of ethylenebutene copolymer in the form of sphericalparticles was obtained (yield 7000 g copolymer/g cat; 1000 kg/g Zr; 1050kg/g MgCl₂) with the following characteristics: MIE=5.9; F/E=41; η=0.8;actual density=0.906; bound butene=15%; insolubles in xylene=88%.

Example 5

In this example a metallocene/TIBAL solution was used in preparation ofthe catalyst.

Preparation of the support

Same procedure as in example 1.

Preparation of the metallocene/TIBAL solution

A 500 cm³ reactor, equipped with anchor stirrer and treated with N₂ at90° C. for 3 hours, was supplied with 382.5 cm³ of a hexane solution ofTIBAL (100 g/liter) and 14.25 g of EBI in N₂ atmosphere, at 20° C. for60 minutes. At the end of this time, a clear solution was obtained.

Preparation of the catalyst

The same reactor was used at the same temperature as in example 1, butwith 110 cm³ of the metallocene/TIBAL solution, the reaction beingconducted for 3 hours instead of 4 hours. 117.5 g of spherical catalystwas obtained, with the following characteristics:

Zr=0.75; Mg=0.14%; Cl=1.54%; Al=1.4%.

Polymerization

The procedure was the same as in example 1, but instead of using 0.1 barof H₂, 0.5 bar of H₂ is used. 175 g of spherical form polyethylene wasobtained (yield 3500 g of polyethylene/g cat; 470 kg/g Zr; 640 kg/gMgCl₂), with the following characteristics:

MIE=17; F/E=31; η=0.9.

Example 6

Polymerization

Using the catalyst of example 5, polymerization was effected accordingto the procedure of example 2 but with the following changes: thecatalyst prepared according to the procedure in example 5 waspre-contacted with 1.45 g of TIBAL instead of 0.42 g of MAO; in theautoclave the 12 pressure was 1 bar instead of 0.1, and 200 g of butenewas loaded instead of 100 grams. 35 g of spherical form ethylene-butenecopolymer was obtained (yield 700 g copolymer/g cat; 127 kg/g MgCl₂),with the following characteristics:

MIE=14; FIE 33; actual density=0.909; bound butene=13%; insolubles inxylene=74%.

Example 7

Preparation of the support

The support was prepared according to the procedure and conditions inexample 1.

Preparation of the metallocene/TIBAL solution

The procedure in example 5 was followed.

Preparation of the catalyst

Preparation was effected with the same procedure as in example 5 butusing 127.5 cm³ of the metallocene/TIBAL solution instead of 110 cm³ andconducting the reaction for 4 hours instead of 3 hours. 117.5 g ofspherical catalyst was obtained with the following characteristics:

Zr=1.02%; Mg=0.16%; Al=1.61%.

Polymerization

The conditions used were the same as in example 1, using the catalystprepared in the manner described previously. 280 g of spherical formpolyethylene was obtained (yield 5600 g polyethylene/g cat) with thefollowing characteristics:

η=1.3; MIE=0,5; F/E=70; Mw/Mn=3,4

Example 8

Preparation of the catalyst

The catalyst was prepared according to the procedure and conditions ofexample 7.

Polymerization

The procedure of example 2 was followed but using 50 g of butene insteadof 100 g and employing the catalyst prepared according to the proceduredescribed above. 220 g of spherical form ethylene-butene copolymer wasobtained (yield copolymer/cat=4400) with the following characteristics:

MIE=5; F/E=31.8; η=1.17; insolubles in xylene=97.4; actualdensity=0.920; C₄ bound=3.9%

Example 9

Preparation of the support

The procedure in example 1 was followed.

Preparation of the metallocene/MAO solution

The procedure in example 1 was followed.

Preparation of the catalyst

The catalyst prepared as in example 1 was washed 3 times with toluene(100 g/liter) at approx. 20° C. The solvent was eliminated under vacuumat a maximum temperature of 40° C.

The obtained spherical catalyst had the following characteristics:Zr=0,45%; Mg=0.26%; Cl=1.22%; Al=2.9%.

Polymerization

Polymerization was conducted in the same conditions as in example 1.112.5 g of spherical form polyethylene was obtained (yield 2250 gpolyethylene/g cat) with the following characteristics:

MIE=0.9; F/E=58; η=1.43.

Example 10

Preparation of the support

The support was prepared according to the method described in example 1.

Preparation of the catalyst

A 1000 cm³ reactor, equipped with anchor stirrer and treated with N₂ at90° C. for 3 hours, was loaded with 500 cm³ of toluene and 6 g of MAOand 50 g of support in N₂ atmosphere, at 20° C. while stirring.

Then the system was heated to 80° C. for 2 hours, after which thesolvent was removed by evaporation at 20 mmHg. The solid obtained wassuspended in 500 cm³ of toluene and 1.2 g of EBI was supplied at 20° C.while stirring. The system was kept in N₂ atmosphere at 20° C. for 6hours.

Then the solvent was removed by vacuum evaporation at 40° C., obtaining57.2 g of catalyst with the following characteristics:

Zr=0.4%; Mg=0.26%; Cl=1.37%; Al=5.2%.

Polymerization

Using the catalyst prepared according to the procedure described above,polymerization was effected in the same conditions as in example 1. 100g of polyethylene was obtained in the form of spherical particles (yield2000 g PE/g catalyst) with the following characteristics:

MIE=0.5; F/E=78; η=1.6.

Example 11

Preparation of the support

The support was prepared according to the method in example 1.

Preparation of the catalyst

A 3000 cm³ reactor, equipped with anchor stirrer and baffles, previouslytreated with N₂ at 90° C. for 3 hours, was supplied at 20° C., whilestirring, in N₂ atmosphere, with 20 g of support, 2000 cm³ of toluene,and 0.914 g of EBI. The mixture was caused to react at 40° C. for 20hours. At the end of this time the solvent was removed by evaporation ata pressure of 20 mmHg, obtaining about 21 g of spherical catalyst withthe following characteristics:

Zr=0.98%; Mg=0.27%.

Polymerization

Using the catalyst prepared according to the method and conditionsstated above, polymerization was effected as in example 1. 160 g ofspherical form polyethylene was obtained (yield 3200 g polyethylene/gcat), with the following characteristics:

MIE=2.96; PE=40.5; η=1.12.

Example 12

Preparation of the support

Preparation was effected similarly to example 1 but instead of supplyingethylene until a yield of 40 g of polymer per g of catalyst wasobtained, the reaction was conducted in such a way as to obtain a yieldof 10 g of polymer per gram of catalyst. 2.9 kg of spherical prepolymerwas obtained, with the following characteristics:

Surface area=2.6 m² /g;

Porosity=1.215 cm³ /g;

P50=79.49 μm;

Ti=0.8%; Cl=4.45%; Mg=1.05%; Al=0.18%.

Preparation of the metallocene/MAO solution

The method and conditions of example 1 were followed.

Preparation of catalyst

Following the procedure in example 1 and using the sup port describedpreviously, 118.2 g of spherical catalyst was obtained with thefollowing characteristics:

Zr=0.44%; Cl=4.16%; Mg=0.95%; Al=5.09%; Ti 0.78%.

Polymerization

Polymerization was effected as in example 1, using the catalystdescribed above. 105 g of spherical form polyethylene was obtained(yield 2100 g polyethylene/g cat), with the following characteristics:

MIE=0.48; F/E=70.

Example 13

Preparation of the support

The procedure as in example 1 was followed, but instead of loading 290 gof catalyst, 96.6 g was loaded, and ethylene was supplied untilconversion polyethylene/cat=100 by weight was obtained. 9.6 kg ofspherical prepolymer was discharged, with the following characteristics:

Surface area=0.9 m² /g (for Hg);

Porosity=0.618 cm³ /g (for Hg);

P50=192.68 μm.

Preparation of the metallocene/MAO solution

The procedure in example 1 was followed.

Preparation of the catalyst

Following the procedure in example 1 and using the support describedpreviously, 118.2 g of spherical catalyst was obtained, with thefollowing characteristics:

Zr=0.41%; Cl=0.66%; Mg=0.072%; Al=4.95%.

Polymerization

Polymerization was effected as in example 1, using the catalystdescribed above. 35 g of spherical form polyethylene was obtained at ayield equal to 700 g polyethylene/g catalyst and with η equal to 1.15.

Example 14

Preparation of the support

The procedure was the same as in example 1 but instead of loading 290 gof catalyst, 48 g was loaded, and ethylene was supplied until a degreeof conversion polyethylene/cat=300 by weight was obtained. 14.4 kg ofspherical prepolymer with the following characteristics was discharged:

Surface area=7 m² /g;

Porosity=0.499 cm³ /g;

P50=392.29 μm.

Preparation of the metallocene/MAO solution

The solution was prepared according to the method in example 1.

Preparation of catalyst

The procedure was as in example 1, using the support described above.18.2 g of spherical catalyst was obtained with the followingcharacteristics:

Zr=0.55%; Cl=0.54%; Mg=0.02%; Al=6.40%.

Polymerization

Polymerization was effected as in example 1 and 35 g of spherical formpolyethylene was obtained with a yield equal to 700 g polyethylene/g ofcatalyst. The polymer had the following characteristics:

MIE=12.6; FIE=23.9; η=0.95.

Example 15

Polymerization

In a glass flask treated with N₂ at 90° C. for 3 hours, 0.216 g ofcatalyst prepared according to the method in example 1 and 6 g of TIBALwere pre-contacted in 50 cm³ of hexane for 5 minutes at 20° C. At theend of this time, the whole was fed into a fluidized-bed gas-phasereactor with a volume of 35 liters, in which 7 bar of ethylene and 8 barof propane were present at a temperature of 75° C. The reaction wasconducted in the gas phase for three hours, keeping the temperature andethylene pressure constant.

At the end it was degassed and 520 grams of spherical polyethylene weredischarged, at yield of 2400 g polyethylene/g catalyst. The bulk densityof the polymer was 0.36 g/cm³ and the flowability 18 sec.

Example 16

Preparation of the support

210 g of a catalyst prepared according to the procedure of Example 1 ofU.S. Pat. No. 4,220,554 was polymerized under the same condition givenin Example 1 (preparation of the support). 8.4 Kg of a prepolymer ingranular form was obtained, having the following characteristics:

Surface area (Hg)=1 m² /g; porosity (Hg, referred to pores with radiusup to 50,000 Å)=0.159 cm³ /g

Preparation of the catalyst

Preparation was carried out under the same conditions of Example 1 butusing 70.9 cm³ of metallocene/MAO solution instead of 200 cm³. About 106g of granular catalyst was obtained with the following characteristics:

Zr=0.1%; Ti=0.05%; Cl=1.28%; Mg=0.38%; Al=1.85%

Polymerization (HDPE)

The above described catalyst was polymerized as described in Example 1.25 g of spherical form polyethylene was obtained (yield 484 gpolyethylene/g cat; 484 Kg/g Zr), with the following characteristics:

η=4.2

Example 17

Preparation of the support

Same procedures as in example 1.

Preparation of the metallocene/TIBAL solution

Preparation was carried out as in example 5 but using 14 g ofbis-(4,7-dimethylindenyl)-zirconium dichloride (BDMI) and 328.8 cm³ of ahexane solution of TIBAL (100 g/l).

Preparation of the catalyst

Using the above described support and metallocene/TIBAL solution,preparation was carried out as in example 1, with the difference that176.7 cm³ of metallocene/TIBAL solution was used. About 110 g ofspherical form catalyst was obtained, with the followingcharacteristics: Cl=1.26%; Mg=0.24%; Ti=0.16%; Al=0.62%; Zr=0.35%

Polymerization

The above described catalyst was polymerized as in example 2, using 50 gof 1-butene instead of 100 g. 185 g of an ethylene-butene copolymer wasobtained (yield 3700 g copolymer/g cat; 1060 Kg/g Zr), with thefollowing characteristics:

MIE=0.45; F/E=24; η=2.18; bound butene=4.2%; actual density=0.9258;insolubles in xylene=99.3%.

Example 18

Preparation of the support

Same procedure as in example 1

Preparation of the metallocene/TIBAL solution

Preparation was carried out as in example 5, but using 15 g ofethylen-bis(4,7-dimethyl indenyl)-zirconium dichloride (EBDMI) and 332cm³ of a hexane solution of TIBAL (100 g/l).

Preparation of the catalyst

Using the above described support and metallocene/TIBAL solution,preparation was carried out as in example 1, with the difference that287.3 cm³ of metallocene/TIBAL solution was used. About 116 g ofspherical form catalyst was obtained, with the followingcharacteristics:

Cl=1.55%; Mg=0.75%; Ti=0.2%; Al=4.05%; Zr=0.75%

Polymerization

The above described catalyst was polymerized as in example 1. 225.9 g ofspherical form polyethylene was obtained (yield 4518 g polyethylene/gcat.; 602 g/g Zr), with the following characteristics:

MIE=2.55; F/E=39.21

Example 19

0.05 g of catalyst of example 18 was precontacted with 0.5 g of TIBAL at20° C. for 5 minutes and then fed to a 4 liters stainless steelautoclave which contained 800 g of propane at 20° C. Ethylene was thefed at 40° C. until 5 g of monomer was absorbed. 0.5 g of modified-MAO(20% solution in Isopar C) was fed and the temperature raised to 75 ° C.Polymerization was carried out under an ethylene partial pressure of 7bar for 1 hour. 395 g of spherical form polyethylene was obtained (yield7452 g polyethylene/g cat.; 1552 Kg/g Zr) which had a bulk density of0.3 g/cm³.

Example 20

Preparation of the support

Same procedure as in example 1

Preparation of the metallocene/MAO solution

Preparation was carried out as in example 1, but using 9 g ofethylen-bis(4,5,6,7-tetrahydroindenyl)-zirconium dichloride (EBTHI) and49.24 g of MAO.

Preparation of the catalyst

Using the above described support and metallocene/MAO solution,preparation was carried out as in example 1, with the difference that170 cm³ of metallocene/MAO solution was used. About 115 g of sphericalform catalyst was obtained, with the following characteristics:

Cl=1.26%; Al=4.2%; Mg=0.28%; Ti=0.16%; Zr=0.33%

Polymerization

The above described catalyst was polymerized as in example 1. 125 g ofspherical form polyethylene was obtained (yield 2520 g polyethylene/gcat.; 763 Kg/g Zr), with the following characteristics:

MIE=68.6; η=0.79

Example 21

Polymerization

0.05 g of the catalyst of example 19 was precontacted with 0.42 g of MAOin 100 cm³ of toluene for 5 minutes at 30° C. The catalyst was fed intoan autoclave previously purged with propylene (3 treatment with 5 bar ofpropylene). 1000 cm³ of H₂ and 2300 cm³ of propylene were fed and thetemperature was set at 70° C. Polymerization was carried out for 2hours. About 330 g of spherical form propylene was obtained (yield 6521g polypropylene/g cat.; 1976 Kg/g Zr) with the followingcharacteristics:

xylene insolubles=74.1%

Example 22

Preparation of the support

Same procedure as in example 1

Preparation of the metallocene/MAO solution

Same procedure as in example 4

Preparation of the catalyst

100 g of the above described support was fed to a 1 liter reactor whichcontained 600 cm³ of toluene. 10 cm³ of diisobutylphthalate was fed at20° C.; the mixture was than heated at 40° C. for 2 hours. 70.5 cm³ ofthe above described metallocene/MAO solution was then fed and themixture was kept at 40° C. for 4 hours under stirring. After removal ofthe solvent under vacuum, 115 g of spherical catalyst was obtained withthe following characteristics:

Zr=0.7%; Al=3.44%; Ti=0.17%; Cl=1.41%; Mg=0.22%

Polymerization

The above described catalyst was polymerized as in example 8. 290 g ofspherical from copolymer (yield 5300 g copolymer/g cat.; 732 Kg/g Zr)was obtained, with the following characteristics:

MIE=0.088; F/E=151.3; η=1.48; actual density=0.910; insolubles inxylene=90.4; Mw/Mn=4.4

Example 23

In a 2.5 l stainless steel reactor the following reactants were fed at30° C.: propane=10 Kg/hr.; TIBAL=33.6 g/hr.; MAO=5.6 g/hr.; catalyst ofexample 1=3 g/hr. The average residence time 7 minutes. The mixture wasthen fed to a fluidized bed reactor having a volume of 350 liters.Polymerization was carried out at 80° C. and 24 bar by feeding propane(23 Kg/hr.), ethylene (15 Kg/hr), butene (5 Kg/hr.).

A spherical form polymer was obtained (yield 6000 g polymer/g cat.),with the following features:

actual density=0.919 g/cm³ ; bulk density=0.363 g/cm³ ; bound butene=6%;insolubles in xylene=95.6%; CC content<5 ppm.

What is claimed is:
 1. A process for the polymerization of CH₂ ═CHRolefins in which R is hydrogen or an alkyl, cycloalkyl or aryl with 1-10carbon atoms comprising:a) preparing a pre-polymer by polymerizing oneor more olefins CH₂ ═CHR, in which R is hydrogen or an alkyl, cycloalkylor aryl with 1-12 carbon atoms, and/or one or more di- or polyenes inthe presence of a coordination catalyst, said coordination catalystcomprising the product obtained by contacting a compound of Ti, V, Zr orHf with a magnesium halide, said magnesium halide being in the form ofparticles having crystallites with an average size below 300 Å, saidmagnesium halide being present in said pre-polymer in an amount ofbetween 50 and 50,000 ppm; b) contacting said pre-polymer with theproduct of the reaction of a compound of a transition metal M selectedfrom Ti, V, Zr and Hf containing at least one M-π bond with anAl-trialkyl compound in which the alkyl groups have from 1 to 12 carbonatoms and linear or cyclic alumoxane compounds containing the repeatingunit --(R₄)AlO--, in which R₄ is an alkyl group with 1-6 carbon atoms ora cycloalkyl or aryl group with 6-10 carbon atoms and containing from 2to 50 repeating units; and c) under conditions effective to polymerize,adding the olefins of formula CH₂ ═CHR to the product of step b).
 2. Aprocess for the polymerization of olefins of the formulae CH₂ ═CHR inwhich R is hydrogen or an alkyl, cycloalkyl or aryl with 1-10 carbonatoms comprising:a) preparing an olefinic pre-polymer containing indispersion a magnesium halide, said magnesium halide being in the formof particles having crystallites with an average size less than 300 Å,and a compound of a transition metal M, chosen from Ti, V, Zr and Hf,containing at least one M-π bond, in which the compound of thetransition metal M is present in a form at least partly combined withthe magnesium halide and in which the atomic ratio M/Mg is greater than0.1; b) reacting the product of step a) with an Al-alkyl compound chosenfrom Al-trialkyl in which the alkyl groups have from 1 to 12 carbonatoms and linear or cyclic alumoxane compounds containing the repeatingunit --(R₄)AlO--, in which R₄ is an alkyl group with 1-6 carbon atoms ora cycloalkyl or aryl group with 6-10 carbon atoms and containing from 2to 50 repeating units; and c) under conditions effective to polymerize,adding the olefins of the formula CH₂ ═CHR to the product of step b). 3.A process for the polymerization of CH₂ ═CHR olefins in which R ishydrogen or an alkyl, cycloalkyl or aryl with 1-10 carbon atomscomprising:a) preparing a pre-polymer by polymerizing with acoordination catalyst of one or more olefins CH₂ ═CHR, in which R ishydrogen or an alkyl, cycloalkyl or aryl with 1-12 carbon atoms, and/orone or more di- or polyenes, said coordination catalyst comprising theproduct obtained by contacting a compound of Ti, V, Zr or Hf with amagnesium halide, said magnesium halide being in the form of particleshaving crystallites with an average size below 300 Å, said magnesiumhalide being present in said pre-polymer in an amount of between 50 and50,000 ppm; and b) contacting said pre-polymer with a transition metalcompound selected from the following compounds:C₂ H₄ (Ind)₂ MCl₂, C₂ H₄(Ind)₂ MMe₂, C₂ H₄ (H₄ Ind)₂ MCl₂, C₂ H₄ (H₄ Ind)₂ MMe₂, Me₂ Si(Me₄ Cp)₂MCl₂, Me₂ Si(Me₄ Cp)₂ MMe₂, Me₂ SiCp₂ MCl₂, Me₂ SiCp₂ MMe₂, Me₂ Si(Me₄Cp)₂ MMeOMe, Me₂ Si(Flu)₂ MCl₂, Me₂ Si(2-Et-5-iPrCp)₂ MCl₂, Me₂ Si(H₄Ind)₂ MCl₂, Me₂ Si(H₄ Flu)₂ MCl₂, Me₂ SiCH₂ (Ind)₂ MCl₂, Me₂ Si(2-Me-H₄Ind)₂ MCl₂, Me₂ Si(2-MeInd)₂ MCl₂, Me₂ Si(2-Et-5-iPr-Cp)₂ MCl₂, Me₂Si(2-Me-5-EtCp)₂ MCl₂, Me₂ Si(2-Me-5-Me-Cp)₂ MCl₂, Me₂Si(2-Me-4,5-benzoindenyl)₂ MCl₂, Me₂ Si(4,5-benzoindenyl)₂ MCl₂, Me₂Si(2-EtInd)₂ MCl₂, Me₂ Si(2-iPr-Ind)₂ MCl₂, Me₂ Si(2-t-butyl-Ind)MCl₂,Me₂ Si(3-t-butyl-5-MeCp)₂ MCl₂, Me₂ Si(3-t-butyl-5-MeCp)₂ MMe₂, Me₂Si(2-MeInd)₂ MCl₂, C₂ H₄ (2-Me-4,5-benzoindenyl)₂ MCl₂, Me₂C(Flu)CpMCl₂, Ph₂ Si(Ind)₂ MCl₂, Ph(Me)Si(Ind)₂ MCl₂, C₂ H₄ -(H₄Ind)M(NMe₂)OMe, isopropylidene-(3-t-butylCp)(Flu)MCl₂, Me₂ C(Me₄Cp)(MeCp)MCl₂, MeSi(Ind)₂ MCl₂, Me₂ Si(Ind)₂ MMc₂, Me₂ Si(Me₄ Cp)₂MCl(OEt), C₂ H₄ (Ind)₂ M(NMe₂)₂, C₂ H₄ (Me₄ Cp)₂ MCl₂, C₂ Me₄ (Ind)₂MCl₂, Me₂ Si(3-Me-Ind)₂ MCl₂, C₂ H₄ (2-Me-Ind)₂ MCl₂, C₂ H₄ (3-Me-Ind)₂MCl₂, C₂ H₄ (4,7-Me₂ -Ind)₂ MCl₂, C₂ H₄ (5,6-Me₂ -Ind)₂ MCl₂, C₂ H₄(2,4,7-Me₃ -Ind)₂ MCl₂, C₂ H₄ (3,4,7-Me₃ Ind)₂ MCl₂, C₂ H₄ (2-Mc-H₄Ind)₂ MCl₂, C₂ H₄ (4,7-Me₂ -H₄ Ind)₂ MCl₂, C₂ H₄ (4,7-Me₂ -H₄ Ind)₂MCl₂, C₂ H₄ (2,4,7-Me₃ -H₄ 1nd)₂ MCl₂, Me₂ Si(4,7-Me₂ -Ind)₂ MCl₂, Me₂Si(5,6-Me₂ -Ind)₂ MCl₂, Me₂ Si(2,4,7-Me₃ -H₄ Ind)₂ MCl₂. wherein M is ametal selected from Tic Zr and Hf; and c) under conditions effective topolymerize, adding the olefins of formula CH₂ ═CHR to the product ofstep b).